1. Field of the Invention
The present invention relates to a component for surface mounting having a surface position to be fixed by adhesive to the surface of another member and to a method for fastening a component for surface mounting with an adhesive.
2. Description of the Prior Art
Components for surface mounting known under the designation SMD (surface mounted device) have been used for several years for hybridization of film circuits. Together with the shift from manual equipping to automatic equipping, the mass employment of SMD components produces a significant boost in economic feasibility. Since an extensive program of components and automatic equipping units is now present, more and more users are switching to the introduction of this formating technology for printed circuit boards as well.
Components for surface mounting are usually taken from a conveying belt, i.e. from a plastic cavity, and are positioned and glued on the surface of another member, for example a printed circuit board. Subsequently, the other member is turned over and, for soldering the component terminals, is dipped into a tin bath or into a solder bath.
A fast and reliable fastening of the components to the other member is acheived from the time the components are positioned until the end of the soldering procedure, i.e. until the solder locations have solidified.
FIG. 1 of the drawings shows how the technological problem thereby occuring has hitherto been resolved. In accordance with the prior art, the following conditions must be observed for reliable gluing of a component for surface mounting:
1. An adhesive compound 3 must be positioned under a housing 1 of the SMD component.
2. The quantity of the adhesive 3 sprayed on must be metered such that, first, the housing 1 of the SMD component and the surface of another member 4 to which the SMD component is to be secured are adequately covered in order to achieve the necessary adhesion of the SMD component and such that, second, the adhesive compound 3 does not cover the solder surfaces of component terminals 2 of the SMD component.
The spacing of the housing 1 of the SMD component from the surface of the other member 4 on which the SMD component is to be secured dare not become excessively large as a consequence of the manufacturing tolerances which unavoidably occur when bending the terminal legs 2 of the SMD component. For example, the spacing of the housing 1 of the SMD component from the surface of the other member 4 on which the SMD component is to be secured amounts to 0.05+0.05 mm.
The overall method for fastening SMD components in accordance with the prior art is very involved so that a reliable adhesion of a SMD component is achieved given a component and given a method of the prior art. The positioning of the adhesive compound 3 under the housing 1 of the SMD component of the prior art requires a relatively great outlay. In accord with the prior art, the adhesive compound 3 must be sprayed on and, as it is sprayed, must also be dosed within relatively narrow tolerances.
The manufacturing tolerances which are unavoidable when bending the terminal legs 2 of the SMD component influence the spacing of the housing 1 from the surface of the other member 4 on which the SMD component is to be fastened. Given a component and given a method of the prior art, the spacing of the housing 1 of the SMD component from the surface of the other member 4 on which the SMD component is to be fixed can only be precisely specified up to these manufacturing tolerances of the terminal legs 2 of the SMD component. Due to this tolerance in the spacing of the housing 1 from the surface of the other member 4, the dosing of the adhesive compound 3 is to come within certain tolerances. This dosing of the adhesive compound 3, namely, depends on the spacing of the housing 1 from the surface of the other member 4 on which the SMD component is to be secured.
When, as a consequence of manufacturing tolerances in the bending of the terminal legs 2 of the SMD component, the spacing of the housing 1 from the surface of the other member 4 on which the SMD component is to be fixed ends up being especially large, it can occur that the dosing of the adhesive compound 3 no longer adequately covers the housing 1 and the surface of the other member 4 to guarantee the required adhesion of the SMD component to the other member 4. When, on the other hand, the spacing of the housing 1 from the surface of the other member 4 is dimensioned very small from the very outset, then for a prescribed dosed quantity of adhesive compound 3 and for some SMD components the surfaces of the terminal legs 2 become covered with adhesive compound 3. As a result, faultless solder locations are no longer possible.